The present invention relates generally to interface devices between humans and computers, and more particularly to computer interface devices that provide force feedback to the user using actuators.
Computer systems are used extensively in many different industries to implement computer controlled simulations, games, and other application programs. More particularly, these types of games and simulations are very popular with the mass market of home consumers. A computer system typically displays a visual environment to a user on a display screen or other visual output device. Users can interact with the displayed environment to play a game, experience a simulation or “virtual reality” environment, or otherwise influence events or images depicted on the screen or in an application program or operating system. Such user interaction can be implemented through a human-computer interface device, such as a joystick, “joypad” button controller, mouse, trackball, stylus and tablet, foot or hand pedals, or the like, that is connected to the computer system controlling the displayed environment. The computer updates the game or simulation in response to the user's manipulation of a moved object such as a joystick handle or mouse, and provides feedback to the user utilizing the display screen and, typically, audio speakers.
Force feedback interface systems, also known as haptic systems, additionally provide force feedback to a user of the computer system. In a typical configuration, a host computer implements software such as an application program, virtual reality simulation, or game and communicates with a connected force feedback interface device. The user grasps a user object of the interface device, such as a joystick, mouse, steering wheel, stylus, etc., and moves the object in provided degrees of freedom. The movement of the user manipulatable object is sensed by the host computer using sensors, and force sensations controlled by the host computer are provided to the user object using actuators of the force feedback interface device. Force feedback can be effectively used to simulate a variety of experiences, including an impact of a surface, a pull of gravity, a crash in a vehicle, a firing of a gun, a bumpy road, etc., and can thus supply the mass market of computer users an entirely new dimension in human-computer interaction.
One problem with existing force feedback systems is that the actuators used in the interface device are expensive and/or inefficient. One common type of actuator used is a DC motor, which is quite bulky and expensive. The cost of the actuators tends to be a significant part of the overall cost of a device, and in the low-cost, competitive consumer market, any unnecessary costs translate into higher costs for the consumer. Other types of actuators used include voice coil actuators, in which a coil is moved through a magnetic field. However, in a voice coil actuator, circuit or wires which supply current to the coil flex with the motion of the coil. Such a flex circuit can be expensive since it must maintain reliability over the life over the actuator. In addition, a coil having current flowing through it tends to build up heat, and this heat may require a large heatsink coupled to the coil to be dissipated properly. If such a heatsink is provided with the moving coil, less efficient heatsinks are used to reduce weight and/or bulk of the moving part. Therefore, more efficient, low cost actuators that provide high fidelity force sensations are desirable for use in mass market force feedback devices.